This invention relates to flexible belts. More particularly it relates to flexible belts fabricated from embedded fibers that are useful for sensing belt properties, such as motion and position.
Electrophotographic printing is a well known and commonly used method of copying or printing original documents. Electrophotographic printing is performed by exposing a light image representation of a desired document onto a substantially uniformly charged photoreceptor. In response to that light image the photoreceptor discharges, creating an electrostatic latent image of the desired document on the photoreceptor""s surface. Toner particles are then deposited onto the latent image to form a toner image. That toner image is then transferred from the photoreceptor onto a receiving substrate such as a sheet of paper. The transferred toner image is then fused to the receiving substrate. The surface of the photoreceptor is then cleaned of residual developing material and recharged in preparation for the production of another image.
Many electrophotographic printers use flexible belts. For example, exposure is often performed on flexible belt photoreceptors, transfer often involves the use of flexible transfer belts, and fusing is often performed using flexible fusing belts. Flexible belts are of two types, seamed or seamless. Seamed belts are fabricated by fastening two ends of a web material together, such as by sewing, wiring, stapling, or gluing. Seamless belts are typically manufactured using relatively complex processes that produce a continuous, endless layer. In general, seamless belts are usually much more expensive than comparable seamed belts. While seamed belts are relatively low in cost, the seam introduces a xe2x80x9cbumpxe2x80x9d that can interfere with the electrical and mechanical operations of the belt. For example, if a seamed belt is a photoreceptor the seam can interfere with the exposure and toner deposition processes, resulting in a degraded final image. It is possible to sense the seam and then synchronize the printer""s operation such that the seam area is not exposed. That is, by knowing the location of the seam it is possible to time printing such that the seam is not imaged.
In the prior art seam sensing was accomplished by locating a xe2x80x9csensing elementxe2x80x9d on the belt and then sensing when that element passes a sensing station. For example, a slot can be formed through a belt and a transmissive electro-optical sensor system can be used to sense that slot. Known alternatives include using a reflector that is sensed by a reflective electro-optical sensor and a magnet that is sensed by a magnetic sensor. However, these prior art techniques either weaken the belt or take up some of the surface area of the belt, thus requiring larger belts.
In addition to tracking the seam area, it can also be beneficial to accurately track the belt""s position over multiple locations and/or to accurately track the belt""s rotation. For example, if multiple color images are to be transferred in close registration it is very important to accurately know where each color image is on the belt. Furthermore, by knowing the belt""s position over time it is possible to accurately determine the belt""s rotational velocity, and thus predict when a given belt location will pass a given point. This is useful in determinative applications wherein a given electrophotographic station (such as exposure, development, or transfer) requires some advance notice before it operates or when belt velocity (or velocity variations) are important. Such applications usually require multiple sensing elements, with the more sensing elements being used the more accurately the belt""s sensed parameters being known. However, locating multiple sensing elements on the belt weakens the belt further or takes up even more of the belt""s surface area.
Electrophotographic printing belts, whether seamless or seamed, are usually comprised of multiple layers, with each layer introducing a useful property. For example, one layer might provide the majority of a belt""s mechanical strength, another might introduce an imaging layer, another might improve a belt""s toner release properties, while yet another might improve thermal insulation. Because multiple layers should be mutually compatible, and since such compatibility significantly limits that range of acceptable materials, manufacturing multiple layer electrophotographic printing belts is challenging.
Given the many application that make use of belt position information, the improved accuracy achievable by using multiple sensing elements, and the difficulty of manufacturing flexible belts a new type of belt having integral sensing elements, would be beneficial.
The principles of the present invention provides for flexible belts having embedded sensor fibers that run across the belt""s width and that can be sensed by a sensor located on the side of the belt.
Electrophotographic machines that use such flexible belts locate sensors along the sides of the belt such that the sensor fibers are sensed. The sensors beneficially produce signals that can be used to determine belt position and/or motion.